In the field of stripping paints, varnishes or lacquers, the current tendency is to develop efficient aqueous formulations using the least possible amount of solvent, in order to limit the effects on the environment. However, the aqueous formulations which are currently developed are relatively inefficient and, for this reason, none of them are mentioned in the Kirk-Othmer Encyclopaedia of Chemical Technology (4th edition, 1996, vol. 17).
International patent application WO/07227 discloses the addition of water to solvent or to mixtures of solvents which are considered to be efficient paint strippers. That document describes compositions containing:
(1) at least one organic solvent chosen from ethyl acetate, methyl ethyl ketone and toluene; PA1 (2) water; PA1 (3) at least one thickener, and PA1 (4) at least one surfactant. PA1 (A) 1 to 100 parts by weight of a mixture (A1) of at least one aromatic solvent chosen from benzaldehyde, toluene, xylene and anisole and (A2) of benzoic acid; PA1 (B) 99 to 0 parts by weight of water; PA1 (A)+(B) representing in total 100 parts by weight. PA1 (A1) aromatic solvent(s): 30-70 parts by weight PA1 (A2) benzoic acid: 0.05-10 parts by weight PA1 (B) water: 30-70 parts by weight. PA1 activators, such as sodium benzoate and, when the aromatic solvent is benzaldehyde, toluene, in a proportion in particular of from 0.1 to 10 parts by weight relative to (A)+(B) (as indicated below, the sodium benzoate also acts as a corrosion inhibitor); PA1 thickeners, such as cellulosic and acrylic thickeners, in a proportion in particular of from 0.1 to 10 parts by weight relative to (A)+(B); as an example of a cellulosic thickener, mention may be made of Methocell 311 sold by the company Dow Chemical Co., whose production process is featured in American patent U.S. Pat. No. 3,388,082 entitled "hydroxypropyl methyl cellulose ethers"; PA1 corrosion inhibitors, such as monoethanolamine, sodium benzoate or citric acid, in a proportion in particular of from 0.1 to 10 parts by weight relative to (A)+(B); PA1 evaporation retardants, such as paraffin, in a proportion in particular of from 0.1 to 10 parts by weight relative to (A)+(B); and PA1 surfactants, such as nonionic surfactants, in a proportion in particular of from 0.1 to 10 parts by weight relative to (A)+(B); as examples of nonionic surfactants, mention may be made of the ethoxylated surfactants of the "Metox" series sold by the company "SEPPIC".
The efficacy of these composition is simply proportional to the amount of organic solvent used and, in any case, is lower than the efficacy of the pure solvent. This is true in particular for toluene, which is the solvent most capable of stripping paints out of the three mentioned.
Moreover, in the case of fully solvent-laden formulations, it is common to use acidic or basic activators, (generally, less than 20% by weight of the total formulation). Among the acidic activators usually found are citric acid, formic acid and acetic acid. Formic acid is the most effective and the one most commonly used (Kirk-Othmer Encyclopaedia of Chemical Technology, 4th edition, 1996, vol. 17). However, this acid can cause serious burns and it is thus of prime importance to develop formulations activated with less corrosive acids.
The aim of the present invention is to propose a composition for stripping paints, varnishes and lacquers which does not have the drawbacks of the prior art.